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Is there a test to rule out the timing chain as the cause of running rough?

When pressing the accelerator, it starts cutting out. It’s worse when it is hot.

Chuck and I have replaced the :
Stromberg Carburetor just rebuilt
The Autolite Distributor just rebuilt
Coil unused
We measured Fuel pump pressure without the support of the electric fuel pump at 6 lbs
Our ignition switch to coil wire is tight and

It idles beautifully. At 378-400 rpm. We set the timing at the tip of the damper pointer.
We adjusted the carburetor jets.

With the car standing still, when I pull on the accelerator rod and slowly rev the engine up, at about an inch or two back, it starts to faulter, stumble and run rough. After the engine got very hot on a very hot day, it had no power when I applied the clutch.

Others are better suited to suggest fixes for engine issues but I wonder about the fuel pressure. If your 6 psi reading is accurate that seems a bit high and I wonder if the carb is getting too much gas and engine is running rich at highway speed. No idea how sensitive your carb might be to a higher pressure but some are and their float valves can be lifted off the seat. Here is a chart from Motors Manual 15th edition which says with the factory installed pump fuel pressure should be a maximum 4 3/4 psi. Unfortunately no chart I have seen - including the few years Packard provided a number - gives a suggested engine RPM to run when checking pressure.

It looks to me like something that is assumed to be OK is not OK.

The engine speed does not have much effect on fuel pressure since the pump can deliver far more fuel than the engine can consume. Even at wide open throttle, fuel pressure should be close to spec, which I think is around 3 PSI for older Packards.

Thanks so much for the specs. We will double check the fuel pressure measurement. We only did one. The mechanical fuel pump is a stock double action fuel pump that was replaced 7 years ago. How can it put out more pressure than designed?

Since the Duchess wasn’t reliable, I rode to the 8th Aanual Orphan Car Exhibit sponsored by Virginia Packard’s and the Lyceum of Alexandria, VA.

We are tackling the problem tomorrow morning at 8 am.
Here are some of the Packards at the show:

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Ok I admit this was dumb. We had pulled out the distributor and changed out the points and condenser. In the process, dropped the screw that held the condenser wire. No problem. I found a replacement with same thread. What didn’t register is that the new screw was a smidgen longer than the original. At higher RPMs, the screw prevented the points from opening as they should. We put in the original distributor which had been out to a shop to press in new bushings. We re-set the timing and used a vacuum gauge to adjust the carburetor jets, getting 18 lbs. it’s running so well and starts up immediately (which was the original problem, hard starting) that we didn’t run another fuel pump pressure test. That stock fuel pump has been on the car 8 years. I can’t imagine it increasing in pressure over time, but if that can happen, please tell me. Very happy camper now. Thanks for your suggestions and guidance.

Sometimes the most obvious thing ends up being the least obvious, or maybe that should be the other way around! In any event, I'm glad you found the problem and no, I don't think that a stock pump will increase its pressure over time.

IT’S ALWAYS SOMETHING DEPT: This morning at Cars ‘n’ Coffee, I was told something was hanging under my car. It was one of the fuel tank support straps, the one on the passenger side, letting the edge of the tank rest on the tailpipe. Guess I’m lucky to be alive. A couple guys got under to assess the situation with me. My friend Chuck ran me home for a drill, a small floor jack, baling wire, and wire cutter. I drilled a hole in the strap, jacked up the tank, threaded the baling wire thru the hole and around the t-bolt. Done. I ordered a new set from Kanter to which I’ll add rolled washers since the strap broke at the head of the t-bolt.

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I’m at the Rockville MD car show. All Packard’s in a line.

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